<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let str = "34567";
        let b = str.match("^\\d{3,5}$")
        console.log("b = ",b)

        // str = "34567&12345";
        // let r = str.replace("\\d{5}","顺子");
        // console.log(r);

    </script>


</body>
</html>